In recent years, the availability of high speed general purpose computing systems and digital video recorders has allowed for the advancement of techniques for detecting and finding scene content in video sequences.
The Fast Fourier Transform (FFT) is a well known and widely used technique for decomposing signals into periodic components and has been employed extensively in the realm of signal processing, to include cases when the signal consists of a single image pixel with time varying amplitude. However, in the case of imagery and video, where CCD arrays can include very large numbers of pixels (e.g., mega-pixels), the FFT method applied to each pixel vector becomes computationally expensive. A large memory buffer would be required in FFT applications to temporal video analysis or similar block processing approaches. Moreover, if the FFT were applied to temporal video analysis, using the full FFT for signals with known a priori periodic structure would result in a significant waste of computation time on irrelevant frequency components. Additionally, the FFT quantizes frequency bins, which could result in the misreporting of desired frequency content leading, in turn, to detection and/or classification errors.
In the communications, optics and signal processing communities, a large body of literature has been presented in general in relation to frequency detection modulation/demodulation [Daniel Zwillinger. CRC Standard Mathematical Tables and Formulae, 31st Edition (Crc Standard Mathematical Tables and Formulae). Chapman & Hall/CRC, 2002; R. Beck, A. G. Dempster, and I. Kale. Finite-precision goertzel filters used for signal tone detection. Circuits and Systems II: Analog and Digital Signal Processing, IEEE Transactions on, 48(7):691-700, July 2001; G Goertzel. An algorithm for the evaluation of finite trigonometric series. The American Mathematical Monthly., 1958; P Mock. Add DTMF Generation and Decoding to DSP-muP Designs, EDN, Mar. 21, 1985, also DSP Applications with the TMS320 Family, Vol. 1. Texas Instruments, 1989], the temporal aspects of video compression codecs [R. Westwater and B. Furht. Three-dimensional dct video compression technique based on adaptive quantizers. Engineering of Complex Computer Systems, 1996. Proceedings., Second IEEE International Conference on, pages 189-198, October 1996], and interferometry using single element detectors [D.-S. Ly-Gagnon, S. Tsukamoto, K. Katoh, and K. Kikuchi. Coherent detection of optical quadrature phase-shift keying signals with carrier phase estimation. Lightwave Technology, Journal of 24(1):12-21, January 2006; Wenwen Liang, Mingxin Qin, Mingke Jiao, HaoYang, Ke Li, Teng Jiao, Liyuan Bai, and Wenyong Wang. Phase detection based on the lock-in amplifier sr844 and experiments of brain neuron cells in mit system. BioMedical Engineering and Informatics, 2008. BMEI 2008. International Conference on, 1:638-642, May 2008; T. Maeno, M. Akiba, N. Hiromoto, and T. Takada. Two-dimensional lock-in amplifier systems for microscopic imaging. Instrumentation and Measurement Technology Conference, 1994. IMTC/94. Conference Proceedings. 10th Anniversary. Advanced Technologies in I & M, 1994 IEEE, pages 536-539 vol. 2, May 1994; M. Nakanishi and Y. Sakamoto. Analysis of first-order feedback loop with lock-in amplifier. Circuits and Systems II: Analog and Digital Signal Processing, IEEE Transactions on, 43(8):570-576, August 1996; W. D. Walker. Sub-microdegree phase measurement technique using lock-in amplifiers. Frequency Control Symposium, 2008 IEEE International, pages 825-828, May 2008; Wei Xu, D. L. Mathine, and J. K. Barton. Analog cmos design for optical coherence tomography signal detection and processing. Biomedical Engineering, IEEE Transactions on, 55(2):485-489, February 2008].
It would be useful to be able to provide scene content detection methods and systems that overcome one or more of the deficiencies of prior approaches to temporal video analysis. It would be useful to be able to perform temporal video analysis (e.g., with each data frame being processed efficiently, in real time, as it is captured) without the need for a large memory buffer as would be required by an FFT or similar block processing approach.